Field of Invention
This invention relates to transistor amplifier circuits and more particularly to such amplifier circuits for providing high-level output with low signal distortion.
Certain known transistor amplifier circuits for operation at high levels of output signal commonly operate with complementary output transistors having collector electrodes connected to the common output node, and with the emitter electrodes connected to the bias supplies. These circuits commonly suffer from thermal run-away which results in excessively high quiescent current in the output transistors as operating temperature increases. One known scheme for correcting this problem includes using low base-emitter bias voltage to bias off the output transistors, even at high operating temperatures. However, such biasing condition of the output transistors contributes high levels of "dead-band" distortion due to the gap in conductivities of the output transistors as they are alternately driven from off to conductive condition by the applied signals.
Alternatively, other known transistor circuits for operation at high levels of output signal include complementary output transistors having the emitter electrodes connected to the common output node, and having collector electrodes connected to the bias supplies. These known circuits introduce high-level distortion attributable to the output level only being able to swing within the limit of the base-emitter junction voltage (Vbe) difference between the bias supply and the reference or ground potential.